Chondrocytes are typically involved in cartilage repair. Cartilage is a structural support tissue that is found in the body in three main varieties. Hyaline, or articular cartilage, helps dissipate loads in joints. In articular cartilage, chondrocytes are encapsulated in a woven, mesh-like matrix of type II collagen and proteoglycans. Elastic cartilage provides flexible support to external structures, and is composed of chondrocytes embedded in a matrix of collagen and elastic fibers. Fibrocartilage aids in transferring loads between tendons and bone. It consists of an outer layer of collagen and fibroblasts that support and inner layer of chondrocytes that make type II collagen fibers.
To date chondrocytes have been used to correct or repair cartilaginous defects. For example, by placing chondrocytes into hydrogels and injecting the chondrocytes into a cartilage defective region. The chondrocytes are used to express matrix proteins required for cartilage repair. Although chondrocytes have been cultured and placed into substrates such as hydrogels, for treatment, or repair of cartilage or bone defects, there is no teaching in the art that chondrocytes can be used to express therapeutic agents for the treatment of pathologies or injuries other than cartilage tissue.
Accordingly, a need exists for using chondrocytes to deliver therapeutic agents to tissue or organs within the body, and particularly to an environment that is not usually associated with chondrocytes. A need also exists for using an implant comprising genetically altered chondrocytes that can locally express and release therapeutic agents into a target region or environment. A further need exists for using chondrocytes as a large scale manufacturing source for therapeutic agents.